Ignition system



Sept. 6, 1955 M. w. SIMS ET AL 2,717,335

IGNITION SYSTEM Filed July 17, 1952 Inventor-s: Marion W- Sims, Ezra G.Hill,

Aaron M. Krakower,

b WW

Then- Attorne g.

United States Patent IGNITION SYSTEM Marion W. Sims, Ezra C. Hill, andAaron M. Krakower, Fort Wayne, Ind., assignors to Genera! Electric Company, a corporation of New York Application July 17, 1952, Serial No.299,416

26 Claims. (Cl. 315-183) This invention relates to electrical sparkignition systems, and more particularly to a capacitor dischargeignition system having a low resistance transformer.

The system, originally employed and adapted for use in connection withaircraft gas turbines or jet engines where difficulty has heretoforebeen experienced in igniting the fuel mixture at high altitude and highair speed, is also applicable to domestic oil burners, stationary gasturbines and the like. Although it has been found that high energycapacitor discharge spark ignition is better suited to effecting fuelignition than are conventional inductive spark systems, prior capacitordischarge systems known to applicants have been found inadequate in oneor more respects. For example, the ignition ability or the ability ofthe prior systems to ignite reliably a fuel mixture under adverseconditions of temperature, pressure, velocity of fuel mixture, andvarious other properties of the fuel mixture has not been suflicientlyhigh to meet the present day trend toward ever increasing air speeds andflying altitudes. Furthermore, there is a need for greater flexibilityin the range of igniter electrode gap spacings which may be employed inconnection with a given system. To be more specific, some presentlyknown capacitor discharge systems, if designed for an igniter plug of agiven spacing, do not operate properly with an igniter plug of lessergap spacing because the unit does not reach full storage capacitorcharge before discharging through the lesser gap spacing as it did inthe case of the greater gap spacing for which it was designed. Inaddition, in some presently known capacitor discharge systems the maindischarge current producing the arc at the igniter electrodes is firstrequired to pass across a series discharge gap, resulting in a divisionof the energy stored in the capacitor between the series gap, whereenergy there released is not elfective in producing ignition, and themain ignition electrodes. Another disadvantage of existing systems isthe high voltampere input required. A further disadvantage is the lowpercentage of the stored capacitor energy delivered to the igniterelectrodes in producing the spark.

It is therefore an object of this invention to provide a new andimproved electric spark ignition system or apparatus of the capacitordischarge type.

It is also an object of this invention to provide an ignition system inconnection with which the capacitor discharge circuit thereof hasespecially low electrical losses compared to prior art circuits of thistype.

It is a further object of this invention to provide a combination pulsetransformer and low loss energy storage reactor suitable for employmentin the capacitor discharge circuit.

Another object is to provide a capacitor discharge ignition systemrequiring low volt-ampere input.

Still another object is to provide a capacitor discharge ignition systemin which a high percentage of the energy stored in the capacitor isreleased in the are at the igniter electrodes.

price The invention will be better understood from the followingdescription when taken in connection with the accompanying drawing, andthe scope of the invention will be pointed out in the appended claims.In the drawing, Fig. 1 is a circuit diagram of an electric sparkignition apparatus for system embodying one form of the invention; Figs.2, 3 and 4 show circuit diagrams illustrating other forms of theinvention; Fig. 5 illustrates typical voltage and current curves of themain discharge capacitor employed in the system during a singleoscillatory discharge burst at the igniter plug; and Fig. 6 shows anelevation cross section through the pulse or ionizing transformer of theinvention.

Referring now to the drawing, and more particularly to Fig. 1, we haveshown a high reactance, voltage stepup input transformer 10, having asaturable magnetic core 11 which may be provided with a gapped magneticshunt 12 between primary and secondary winding receiving sections. Aprimary winding 13 is connected through a series capacitor 14 toconductors 15 and 16, which are in turn connected, for example, to a 115volt- 400 cycle source of power, while the terminals of a main dischargeand energy storage capacitor 17 are connected to a secondary winding 18through a suitable rectifier 19 which may be of the selenium type. Thecapacitor 14, series connected in one of the power conductors to theprimary winding of the transformer, serves to limit circuit currents tosafe values for the circuit elements, in addition to other purposes tobe discussed hereinafter. The transformer it and rectifier 19 constitutea direct current supply to charge the main discharge capacitor 17 and atriggering or auxiliary capacitor 20, the latter through a resistor 21,the combination being in shunt circuit relationship to the maindischarge capacitor 17. in accordance with the invention, the triggeringcapacitor 20 is provided with a triggering discharge circuit whichincludes in series circuit relation the primary winding 22 of our newand improved volt age step-up pulse or ionizing and storage inductortransformer 23, to be discussed in detail hereinafter, and a dischargegap 24 or other suitable circuit completing triggering device. The maindischarge circuit of capacitor 1'7 is shown in heavy lines and includesin series circuit relation the secondary winding 25 of the ionizingtransformer and a main ignition gap defined by ignition electrodes 26and 27 of igniter plug 28. It should be noted that device 24 is notincluded in the main discharge circuit of the main discharge capacitor17,

The transformer 10 steps the power voltage up to approximately 1500volts, for example, and this transformer in conjunction with seriescapacitor 14 forms a partial voltage stabilizer, with the added featurethat on secondary short circuit the capacitor limits the short circuitcurrent to a safe value for the rectifier 19 and other circuit elements.Thus, capacitor 14 limits the current drawn from the 400 cycle source,particularly during discharge and recharge of capacitor 1'7, withoutintroducing losses, and in addition helps control the charging rate ofcapacitors 17 and 20 and produces in combination with the non-linearmagnetizing reactance of transformer 10 a stabilizing effect tending tominimize fluctuations in output voltage of transformer 10 duringfluctuations in source voltage. This latter effect is produced by havingthe capacitive reactance of capacitor 14 greater than the unsaturatedmagnetizing reactance of transformer 10. Furthermore, the capacitor 14helps to correct the lagging power factor resulting from the transformerreactance, thus minimizing required input voltamperes. Transformer 10 ispreferably a high leakage reactance transformer operated at a fluxdensity such that the core is somewhat saturated.

The capacitor 2t and resistor 21 constitute a timing circuit whichtogether With transformer i capacitor 14, and capacitor 17 fix thefiring rate of the unit while the capacitor 17 and the secondary 25 ofionizing transformer 23 comprise a damped series resonant circuit whenthe gap defined by electrodes 26 and 27 is SlliTlCiCl'lilj ionized to beelectrically conducting.

Upon application of voltage to the circuit, charges build up oncapacitors l7 and 29, with the charging of capacitor being slowed to thedesired extent by making the charging current flow through resistor 21.When the voltage across capacitor 29 reaches the break-down value of gap24, at which time the voltage of capacitor 17 is still substantiallylower than that required to ionize the gap between electrodes 26 and 27,gap 24 arcs over and in efect becomes a short circuit. Since theinternal resistance of the gap immediately becomes quite low once itbreaks down, this instantaneously applies the full voltage of capacitor26 to the primary 22- of the ionizing transformer 23, with the resultthat a high voltage is induced in the secondary 25. This high voltageproduces ionization of the gas between the electrodes 26 and 27 of plug28, causing arc over and thus completing the circuit comprising the mainstorage capacitor 17, the secondary 25 of the ionizing transformer, andthe gap of the igniter plug 23. At this point in the operation the maincapacitor 17 takes over and delivers its charge to the secondary 25 oftransformer a3 and the gap defined by electrodes 26 and 27 of plug 28.That portion of the energy delivered to the gap is effective inproducing ignition of a fuel-air mixture at the gap, and since theionizing transformer serves also as a storage inductor, the remainingenergy is stored in the ionizing transformer. The inductor, or ionizingtransformer, then discharges, continuing the delivery of energy to thegap and recharging the capacitor 17 in the opposite polarity with theenergy not already consumed, thus completing the first half cycle of anoscillatory discharge of capacitor 1?. Oscillation in thisinductance-capacitance-spark gap circuit continues, damped only by thespark gap and unavoidable circuit losses, until the original storedenergy is dissipated, a large portion of it having been delivered to thearc itself where it is effective in producing ignition. Dun ing theoscillatory discharge, the voltage induced in the primary 22 of theionizing transformer is too low to restrike the arc in gap 2 so there isno dissipation of energy in the trigger gap.

From the instant the main ignition gap at the plug 28 breaks down, theperformance of the discharge circuit similar to that of a seriesrcsistance-inductance-capacitance circuit with an initial charge on thecapacitor. Such a circuit will oscillate until substantially all theoriginal stored energy is dissipated in the circuits dissipativeelements. Thus, duration of the oscillatory burs f depends on the totaleffective resistance in the discharge circuit, a typical duration beingfive or six pulses, as illustrated by Fig. 5 where the main dischargecapacitor current and voltage are plotted against time to define currentcurve 29 and voltage curve 30 during one oscillatory discharge burst.After the burst, the capacitors re-charge and the above describedphenomenon repeats at a repetition rate determined by the elements whichinfluence capacitor charging time, and by the operating voltage of thetriggering device.

Since the effective resistance of a short are suitable for ignitionpurposes is low, it is imperative that other resistances in the circuitbe extremely low. Otherwise such resistances would consume the energywithout contributing to ignition. Thus, an important feature of theignition system of the invention is low resistance of that portion ofthe circuit shown in bold or heavy lines in Figs. 1, 2, 3 and 4, and ournew and improved low resistance ionizing and storage inductortransformer 23 makes a low overall circuit resistance possible.Specifically, the circuit resistance of the main discharge circuit,including the resistance of the conductors and connections, of theionizing transformer secondary measured at a frequency and voltage equalto that occurring during the oscillation of a discharge burst, and thatof capacitor 17 measured under the same conditions, but not includingresistance of the are between igniter electrodes 26 and 27, should beless than 1 ELK/E E C the efinitions of which symbols will be describedhereinafter.

The ionizing transformer-storage inductor may be either of theautotransforrner type or of the insulating type. It is proportioned tohave the properties of a good pulse transformer, while at the same timehaving the properties of a good low loss, low reactance storageinductor. Since these requirements conflict to some degree, it is anobject of this invention to provide an optimum compromise. One methodwhich we have found satisfactory for constructing the ionizingtransformerstorage inductor is illustrated in Fig. 6 where the numeral31 identifies a high permeability inner core, which may be made offerrite material, surrounded by a coil 32 which may be either layerwound with magnet wire or spirally wound with strip copper. The coil 32is pro vided with a high voltage secondary lead 33 for connection toelectrode 27 of plug 28, low voltage primary leads 34 and 35 and lead 36from the low voltage end of secondary winding 25. The core 31 and coil32 are embedded or molded within suitable insulating material 37 such assolventless varnish or a combination of methyl methacrylate andsolventless varnish as illustrated. in addition, an outer magnetic coreyoke 38 encircling the core, winding and insulating material may also beprovided. For maximum effectiveness as a pulse transformer to producethe initial ionizing spark, the primary and secondary are closelycoupled and a high permeability core is used to assure sufiiciently lowmagnetizing current during induction of the pulse ionizing voltage.

However, in the interest of good ignition ability, the inductance of thetransformer secondary 25, which must have enough turns to produce thehigh ionizing voltage, for example 15,000 volts, must be low enough topermit high values of current to flow during the main discharge. Thislow inductance requirement may also be expressed as a requirement for ahigh natural frequency of oscillation for the main discharge capacitor17 and the transformer secondary 25. This requirement conflicts directlywith that of a high inductance primary with close coupling. In ourinvention this problem is solved by using a core having a high initialpermeability, but one which becomes saturated by the discharge currentof ionizing capacitor 20 after the ionizing voltage has reached a highvalue, thus leaving the inductance low for the immediately followingmain discharge. Operation of the system may be achieved with an ionizingcapacitor 20 of value low enough not to be capable of saturating primary22, by permitting the core saturation to be delayed until the maindischarge current has reached saturation value, but our results showsuperior performance and better reliability when the capacitor 20 islarge enough to produce core saturation immediately following theionizing pulse.

Making the final inductance or saturated condition of secondary 25 toolow will result in main discharge currents so high that the IR drops inthe circuit conductors are appreciable in comparison with the arcvoltage between electrodes 26 and 27, and consequently in theconsumption of an appreciable portion of the energy initially stored incapacitor 17 as 1 R losses not contributing to ignition. On the otherhand, making this inductance too high reduces the peak rate of energyrelease in the spark burst and lengthens the duration of the burst tosuch an extent that energy is not delivered to the spark at a highenough rate to produce ignition, even though a high percentage of theinitial stored energy may be eventually released in the are. We findthat where L is the inductance in henries of secondary 25 with the coreremoved, which is approximately its inductance with its core in thesaturated condition; R is the total series resistance in ohms in theloop comprising 17, secondary 25, and the igniter plug, includingresistance of the conductors and connections but not including that ofthe gap; E is the initial voltage in volts on 17 at the start of thedischarge; C is the capacitance of 17 in farads, and Earc is the voltagein volts between 26 and 27 when the arc current is equal to henries6,000,000C

henries Furthermore, we find that the inductance of L5 of the secondarywinding as measured with the core in place and with very low currentflowing should be at least two times as high as the value measured witha direct current of This ratio is determined primarily by the propertiesand proportions of the core.

Mutual inductance between primary winding 22, whose self inductance is Lwith core unsaturated, and the secondary winding 25, whose inductance isL5 with core unsaturated, should be greater than .1'\/LpLs and nearly aspractical to /L Ls. In other words, the primary and secondary windingsshould be relatively closely coupled.

The distributed capacitance between turns and layers of secondary 25should ideally be zero, but in no case should it constitute theequivalent of a lumped capacitance across the winding of more than whenNp and NS are respectively the number of turns in primary and secondarywindings, and C20 is the capacitance of the ionizing capacitor 20. Thisdistributed capacitance is controlled by the spacings, and by dielectricconstants of the insulation, between turns and layers of winding 25.

The modification shown in Fig. 2 differs from Fig. 1 in that the maincapacitor discharge current goes through the entire transformer windingWhereas in Fig. 1 it does not go through the primary winding 22. In bothfigures, the transformer 23 is shown autotransformer connected. In Fig.l voltage applied to electrodes 26-27 is the sum of the voltage inducedin Winding 25 and the voltage on capacitor 17. In Fig. 2 this appliedvoltage is the sum of the voltages induced in windings 22 and 25 plusthe voltage on capacitor 17, and is therefore higher than in Fig. 1.However, the higher inductance in the main discharge circuit of Fig. 2reduces the peak value of the discharge current and prolongs the burst.

In Figs. 3 and 4 the transformer 23 is shown connected as a conventionaltransformer and the ionizing voltage applied to electrodes 26 and 27 isonly that of secondary winding 25 plus that of capacitor 17.

Fig. 4 differs from Fig. 3 in that the relative positions of the primarywinding 22 and the triggering capacitor 20 are reversed in the localloop circuit including them and the triggering device 24. Fig. 3 ispreferable from the standpoint of minimizing insulation requirements intransformer 23, whereas Fig. 4- has the desirable feature thatcapacitors 17 and 2d may have one common plate. Fig. 1 has both theseadvantages.

While we have in accordance with the patent statutes shown and describeda particular embodiment of our invention and modifications thereof, itwill be obvious that changes and other modifications can be made withoutdeparting from the invention in its broader aspects, and we, therefore,aim in the appended claims to cover all such changes and modificationsas fall Within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A capacitor discharge ignition system comprising, in combination, asource of unidirectional voltage capacitor-charging current, a mainenergy storage capacitor connected across said source, a triggeringcapacitor connected to be charged through a resistor by said source, avoltage step-up transformer having a low voltage primary winding and ahigh voltage secondary winding, a circuit completing triggering deviceconnected to discharge said triggering capacitor through said lowvoltage primary winding when the voltage charge on said triggeringcapacitor attains a predetermined value, said transformer having atleast said secondary winding connected directly in series with said maincapacitor forming a discharge circuit, said discharge circuit beingadapted to be connected directly to an ignition gap.

2. A capacitor discharge ignition system comprising, in combination, asource of unidirectional voltage capacitor-charging current, a mainenergy storage capacitor connected across said source, a triggeringcapacitor connected to be charged through a resistor by said source, avoltage step-up transformer having a low voltage primary winding and ahigh voltage secondary Winding, a trigger gap connected to dischargesaid triggering capacitor through said low voltage primary winding whenthe Volt age charge on said triggering capacitor attains a predeterminedvalue, said transformer having at least said secondary Winding connecteddirectly in series with said main capacitor forming a discharge circuit,said discharge circuit being adapted to be connected directly to anignition gap.

3. A capacitor discharge ignition system comprising, in combination, asource of unidirectional voltage capacitor-charging current, a mainenergy storage capacitor connected across said source, a triggeringcapacitor connected to be charged through a resistor by said source, avoltage step-up autotransformer having a saturable magnetic coreprovided with a low voltage primary Winding and a high voltage secondarywinding, a sealed trigger gap connected to discharge said triggeringcapacitor through said low voltage primary Winding when the voltagecharge on said triggering capacitor attains a predetermined value, saidautotransformer having at least said secondary winding connecteddirectly in series with said main capacitor forming a discharge circuit,said discharge circuit being adapted to be connected directly to anignition gap.

4. A capacitor discharge ignition system comprising, in combination, alow voltage input terminal for connection to a source of direct current,a high voltage output terminal for connection to an ignition gap, and acommon terminal for connection to both said source and gap,

' a transformer having a high voltage secondary winding and a lowvoltage primary winding, said transformer having at least said highvoltage secondary winding connected directly between said input andoutput terminal, a main capacitor connected across said input and commonterminals, an auxiliary capacitor and a circuit completing triggeringdevice, means for serially connecting said primary winding, saidauxiliary capacitor and said circuit completing triggering device in aclosed local circuit, a charging resistor for connecting a junctionbetween two elements in said local circuit to said common terminal, andmeans for connecting another junction in said local circuit to saidinput terminal.

5. A capacitor discharge ignition system comprising, in combination, alow voltage input terminal for connection to a source of direct current,a high voltage output terminal for connection to an ignition gap, and acommon terminal for connection to both said source and gap, atransformer having a saturable magnetic core provided with a highvoltage secondary winding and a low voltage primary winding, saidtransformer having at least said high voltage secondary windingconnected directly between said input and output terminals, a maincapacitor connected across said input and common terminals. an auxiliarycapacitor and a sealed trigger gap, means for serially connecting saidprimary winding, said auxiliary capacitor and said tr' gap a localcircuit, a charging resistor for connecting the junction between saidtrigger gap and said auxiliary capacitor in local circuit to said commonterminal, and means for connecting another junction of said localcircuit to said input terminal.

6. A capacitor discharge ignition system comprising, in combination, alow volta e input terminal for connection to a source of di ect current,a high voltage output terminal for connection to an ignition gap, and acommon terminal for connection to both said source and gap, anautotransformer having a saturable magnetic core provided with a highvoltage secondary winding and a low voltage primary winding, saidautotransformer having at least said high voltage secondary Windingconnected directly between said input and output terminals, a maincapacitor connected across said input and common terminals, an auxiliarycapacitor and a sealed trigger gap, means for serially connecting saidprimary winding, said auxiliary capacitor and trigger gap in a closedlocal circuit, a charging resistor for connecting the junction betweensaid trigger gap and said auxiliary capacitor in said local circuit tosaid common terminal, and means for connecting the junction between saidauxiliary capacitor and primary winding in said local circuit to saidinput terminal.

7. In an electric spark ignition apparatus for supplying a recurrent arcdischarge between a pair of ignition electrodes, a pair of effectivelyunidirectional current supply conductors, a main capacitor connectedacross said conductors, an auxiliary capacitor and a current limitingresistor serially connected across said conductors, a spark dischargedevice including a pair of sparking electrodes disposed in spaced apartrelation in a sealed envelope, one said sparking electrode beingconnected to the common terminal of said ca acitors, a step-uptransformer having a low voltage primary winding and a high voltagesecondary winding, a main series discharge circuit consisting of saidmain capacitor and said transformer secondary winding directly connectedin series, said discharge circuit being adapted to be directly connectedto said ignition electrodes, and means connecting said primary windingand said spark discharge device across the other of said capacitor in anauxiliary series discharge circuit, whereby discharge of said othercapacitor through said auxilitary series discharge circuit triggers saidmain series discharge circuit through said transformer.

8. In combination, a voltage stabilizing network having input terminalsfor receiving a variable alternating supply voltage and output terminalsfor delivering a stabilized alternating voltage, and an ignition systemhaving supply terminals connected to said output terminals and highvoltage disch rge current terminals for connection to an ignition gapdevice.

9. ln combi said LiOEl, a vintage stabilizing networi; having inputterminals for receiving a variable alternating supply voltage and outputterminals for delivering a stabilizing alternating voltage, and acapacitor discharge ignition system having supply conductors including arectifier connected to said output terminals and high voltage capacitordischarge current conductors for connection to an ignition gap device.

10. In combination, a high leakage reactance transformer having asaturable magnetic core provided with a primary winding and a secondarywinding, a capacitor having a higher reactance than the unsaturatedmagnetizing reactance of said transformer connected in series with saidprimary winding, a storage capacitor, and half wave rectifier connectedacross said secondary winding, an inductor winding a discharge circuitconsisting of said capacitor and said inductor winding directlyconnected in series, and means for periodically inducing a high voltagepulse in said inductor winding for initiating an oscillatory dischargeof said capacitor through said inductor winding.

11. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a saturable magnetic coreprovided with a low resistance winding having a low voltage primaryterminal, a common terminal and a high voltage secondary terminal fordirect connection to one electrode of an ignition gap device, a maindischarge capacitor and a triggering capacitor having an effectivelycommon terminal directly connected to said common terminal of saidtransformer, said main discharge capacitor having a terminal for directconnection to another electrode of said ignition gap device, saidtriggering capacitor having another terminal, a current limitingresistor directly connected between the other terminals of saidcapacitors, a normally-open circuit-completing triggering deviceconnected between the low voltage primary terminal of said transformerand said other terminal of said triggering capacitor, and meansconnected to the terminals of said main discharge capacitor for chargingboth of said capacitors.

12. In a capacitor discharge ignition system, a combined ionizingautotransformer and series inductor having a saturable magnetic coreprovided with a low resistance winding having a low voltage primaryterminal, a common terminal, and a high voltage secondary terminal fordirect connection to one electrode of an ignition gap device, a maindischarge capacitor and a triggering capacitor each having a pair ofterminals, one terminal of said main discharge capacitor being directlyconnected to the low voltage primary terminal of said autotransformerwinding, one terminal of said triggering capacitor being directlyconnected to the common terminal of said autotransformer winding, meansfor directly connecting the other terminal of said main dischargecapacitor to another electrode of said ignition gap device, a resistordirectly connected between the other terminal of the triggeringcapacitor with the other terminal of the main discharge capacitor, anormally-open circuit-completing triggering device having two terminals,one of which is directly connected to the junction between said maincapacitor and said low voltage primary winding and the other terminal ofwhich is directly connected to the junction between said resistor andthe other terminal of said triggering capacitor, and means connected tothe terminals of said main discharge capacitor for charging both of saidcapacitors.

13. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a saturable magnetic coreprovided with a primary winding and a secondary winding each having apair of terminals, a main discharge capacitor having a pair of terminalsone of which is directly connected to one terminal of each of saidwindings, the other terminal of said secondary winding being for directconnection to an ignition gap device, a triggering capacitor having apair of terminals, one of which is directly connected to the otherterminal of said primary winding, a resistor directly connected betweenthe other terminals of said capacitors, a normallyopencircuit-completing triggering device connected in shunt circuit relationwith said primary winding and said triggering capacitor, and meansconnected to the terminals of said main discharge capacitor for chargingboth of said capacitors.

14. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a saturable magnetic coreprovided with a primary winding and a secondary winding, a maindischarge capacitor having a pair of terminals one of which is directlyconnected to a terminal of said secondary winding, a triggeringcapacitor directly connecting one terminal of said primary winding tothe directly interconnected terminals of said main discharge capacitorand said secondary winding, a normally-open circuit-completingtriggering device connected between the directly interconnectedterminals of said main discharge capacitor and said secondary windingand the remaining terminal of said primary winding, a current limitingresistor directly connected between the remaining terminal of said maindischarge capacitor and said remaining terminal of said primary winding,and means connected to the terminals of said main discharge capacitorfor charging both of said capacitors.

15. In a capacitor discharge ignition system, a low resistanceoscillatory main discharge circuit for connection to an ignition gapdevice consisting of a capacitor, an inductor, and conductor leads fordirectly connecting said capacitor and inductor in series to such a gap,the resistance R of said circuit measured at a frequency and voltageequal to that occurring during an oscillatory discharge burst of saidcircuit being less than where L and C are respectively the inductance inhenries of the inductor and the capacitance in farads of the capacitorwhen measured under the same conditions as said resistance, E is theinitial voltage in volts on the capacitor at the start of the discharge,and Ears is the voltage in volts of the gap arc discharge when the arccurrent is equal to C NEW 16. In a capacitor discharge ignition system,a low resistance oscillatory main discharge circuit for connection to anignition gap device consisting of a capacitor, an inductor, andconductor leads for directly connecting said capacitor and inductor inseries to such a gap, the inductance L of said inductor measured at afrequency and voltage corresponding to that occurring during anoscillatory discharge burst of said circuit being greater than W henriesand less than where R and C are respectively the resistance in ohms ofsaid circuit and the capacitance in farads of said capacitor whenmeasured under the same conditions that the inductance of said inductoris measured under, E is the initial voltage in volts on said capacitorat the start of a discharge burst, and Ears is the voltage in volts ofthe gap arc discharge when the arc current is equal to ohms henries 10the inductance L of said inductor measured at a frequency and voltagecorresponding to that occurring during an oscillatory discharge burst ofsaid capacitor being greater than R E C' m henries and less than arccurrent is equal to 18. In a capacitor discharge ignition system, a lowresistance oscillatory main discharge circuit consisting of a capacitorand a saturable core inductor directly connected in series, saiddischarge circuit being adapted to be directly connected to an ignitiongap device, said inductor being proportioned to saturate its core at avalue of discharge current equal to so as to reduce its inductance atsaid value of current to less than half its unsaturated core inductancewhere C is the capacitance of the capacitor in farads, L is the air coreinductance of said inductor, and E is the initial voltage in volts onsaid capacitor at the start of the discharge.

19. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a secondary winding forconnection in series circuit including a main discharge capacitor and anignition a'rc gap device, said transformer-inductor having a saturablemagnetic core, said secondary winding having a value of saturated coreinductance L which is greater than W henries and less than 6,000,0000hennes the arc current is as L the unsaturated core inductance LS of thesecondary Winding being at least twice the saturated core inductance L.

20. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a secondary winding forconnection in series circuit including a main discharge capacitor and anignition arc gap device, said transformer-inductor having a saturablemagnetic core and a primary winding, the mutual inductance between theprimary winding whose self inductance is Lp with the core unsaturatedand the secondary winding whose self inductance is Ls With the coreunsaturated being between \/Lp Ls and .1 /L L3.

21. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a secondary winding forconnection in a series circuit including a main discharge capacitor andan ignition arc gap device and having a primary Winding for connectionto a triggering capacitor, the distributed ca- 11 pacitance betweenturns and layers of said secondary winding being less than where Np andNS are respectively the turns of said prirnary and secondary windingsand C20 is the capacitance of said triggering capacitor in farads.

22. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a secondary Winding forconnection in a series circuit including a main discharge capacitor andan ignition arc gap device, said transformer-inductor also having asaturable magnetic core and a primary winding, said secondary windinghaving a value of saturated core inductance L which is greater than WWhenries and less than 6,000,0000 where R is the resistance of thecircuit exclusive of the gap in ohms, E is the initial voltage in voltson the capacitor at the start of the discharge, C is the capacity of thecapacitor in farads, Earc is the arc volttage when the arc current isthe unsaturated core inductance Ls of the secondary winding being atleast twice the saturated core inductance L, the mutual inductancebetween the primary winding whose self inductance is Lp with the coreunsaturated and the secondary winding whose self inductance is Ls withthe core unsaturated being between \/Lp Ls and 23. In a capacitordischarge ignition system, a combined ionizing transformer and seriesinductor having a secondary winding for connection in a series circuitincluding a main discharge capacitor and an ignition arc gap device,said transformer-inductor having a saturable magnetic core and a primarywinding for connection to a triggering capacitor, said secondary windinghaving a value of saturated core inductance L which is greater thanhenries 100 E my and less than where R is the resistance in ohms of thecircuit exclusive of the gap, E is the initial voltage in volts on themain discharge capacitor at the start of the discharge, C is thecapacity of the main discharge capacitor in farads, Earc is the arcvoltage when the are current is the unsaturated core inductance L5 beingat least twice the saturated core inductance L. the distributedcapacitance between turns and layers of said secondary w1ndhenriesincluding a main discharge capacitor and an ignition arc gap device,said transformer-inductor also having a saturable magnetic core and aprimary winding for connection to a triggering capacitor, mutualinductance between the primary winding whose self inductance is Lp withthe core unsaturated and the secondary winding self-inductance is Lswith the core unsaturated being between the '\/Lp Ls and .l'\/Lp Ls, thedistributed capacitance being less than where Np and NS are respectivelythe turns of said primary and secondary windings and C20 is thecapacitance of said triggering capacitor in farads.

25. In a capacitor discharge ignition system, a combined ionizingtransformer and series inductor having a secondary winding forconnection in a series circuit including a main discharge capacitor andan ignition arc gap device, said transformer-inductor also having asaturable magnetic core and a primary winding for connection to atriggering capacitor, said secondary winding having value of saturatedcore inductance L which is greater than RZEZC 0 0) henries and less thanwhere R is the resistance in ohms of the circuit exclusive of the gap, Eis the initial voltage in volts on the main discharge capacitor at thestart of the discharge, C is the capacity of the main dischargecapacitor in farads, Earc is the arc voltage when the arc current is CMl the unsaturated core inductance Ls of the secondary winding being atleast twice the saturated core inductance L, the mutual inductancebetween the primary winding whose inductance is Lp with the coreunsaturated and the secondary winding being between \/Lp Ls and .l\/LpLs, the distributed capacitance between turns and layers of saidsecondary Winding being less than henries References Cited in the fileof this patent UNITED STATES PATENTS 1,312,497 Cavanagh Aug. 5, 19191,729,492 Sauer Sept. 24, 1929 1,799,011 Fitzsimmons et a1. Mar. 31,1931 2,239,002 Hall Apr. 22, 1941 2,395,629 Kongsted Feb. 26, 19462,497,307 Lang Feb. 14, 1950 2,551,101 Debenham et al. May 1, 1951

